Method of Joining Pipes in End to End Relation

ABSTRACT

A method for connecting pipe elements together end to end. The method includes providing a coupling having a plurality of segments with at least one camming surface, the segments being joined end to end by a plurality of adjustably tightenable fasteners, positioning a first and a second of the pipe elements in end to end relation, positioning the segments surrounding the ends of the pipe elements, engaging the camming surfaces on the segments with grooves on the pipe elements and tightening the fasteners so as to draw the segments toward one another. The camming surfaces slide into the grooves and move the first and second pipe elements away from one another.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/091,216 filed Mar. 28, 2005, which claims priority to U.S.Provisional Application No. 60/556,962, filed Mar. 26, 2004.

FIELD OF THE INVENTION

The invention concerns a method of using couplings for joining pipes inend to end relation and effecting a substantially rigid or a flexiblefluid tight joint therebetween.

BACKGROUND OF THE INVENTION

Couplings for joining pipes together end to end comprise arcuatesegments that circumferentially surround co-axially aligned pipes andengage circumferential grooves positioned proximate to the ends of eachpipe. The couplings are also used to connect pipes to fluid controlcomponents such as valves, reducers, strainers, restrictors, pressureregulators, as well as components to components. Although in thedescription which follows pipes are described, they are used by way ofexample only, the invention herein not being limited for use only withpipes per se. It should also be noted that the term “pipe” as usedherein refers to straight pipes as well as elbows, tees and other typesof fittings.

The segments comprising the couplings have circumferential keys thatextend radially inwardly toward the pipes and fit within the groovesaround the pipes. The keys are typically somewhat narrower than thegrooves to permit them to fit within the grooves and bear against theshoulders formed by the grooves to hold the pipes together againstinternal pressure and external forces that may be applied to the pipes.External forces may arise due to thermal expansion or contraction of thepipes due to changes in temperature as well as the weight of the pipesor components such as valves attached to the pipes, which can besignificant for large diameter pipes and valves. Wind loads and seismicloads may also be a factor.

It is advantageous that pipe couplings be substantially rigid, i.e.,resist rotation of the pipes relative to one another about theirlongitudinal axes, resist axial motion of the pipes relatively to oneanother due to internal pressure, and resist angular deflection of pipesrelative to one another. A rigid coupling will be less likely to leak,requiring less maintenance, and will simplify the design of pipingnetworks by eliminating or at least reducing the need for engineers toaccount for axial motion of pipes in the network when subjected tosignificant internal pressure. Pipes joined by rigid couplings requirefewer supports to limit unwanted deflection. Furthermore, valves andother components which may tend to rotate out of position because theircenter of gravity is eccentric to the pipe axis will tend to remain inposition and not rotate about the longitudinal axis under the pull ofgravity when the pipe couplings are substantially rigid.

Many couplings according to the prior art do not reliably provide thedesired degree of rigidity mainly because they use keys havingrectangular cross-sections that are narrower than the width of thegrooves that they engage. This condition may result in inconsistentcontact between the coupling and the pipes which allows too much freeplay and relative movement, for example, axially, rotationally orangularly, between the pipes. It is also difficult to ensure that suchkeys properly engage the grooves. Couplings which provide a more rigidconnection may be ineffective to force the pipe ends apart at a desireddistance from one another so that the keys and grooves are in properalignment and the pipes are properly spaced. When properly spaced apart,the pipe ends and the coupling cooperate with a sealing memberpositioned between the coupling and the pipe ends to ensure a fluidtight seal. The movement of the pipes, although small, is effected asthe couplings are engaged with each other and the pipe and may requirethat significant torque be exerted upon the fasteners used to clamp thecoupling to the pipes. This is especially acute when pipes to be joinedare stacked vertically one above another, and the action of engaging thecoupling with the pipes must lift one of the pipes upwardly relativelyto the other in order to effect the proper spacing between the pipeends. For such couplings, it is also difficult to reliably visiblyensure that the couplings have been properly installed so that the keysengage the grooves and the pipes are spaced apart as required to ensurea fluid tight seal.

It would be advantageous to provide a coupling that provides increasedrigidity while also reducing the force necessary to engage the couplingwith the pipe ends to effect their proper spacing, and also provides areliable visual indication that the couplings are properly installed onthe pipes.

SUMMARY OF THE INVENTION

The invention concerns a method for connecting pipe elements togetherend-to-end. The pipe elements have circumferential grooves proximate toeach end. The method comprises:

-   -   providing a coupling comprising a plurality of segments joined        end-to-end by a plurality of adjustably tightenable fasteners,        each of the segments having a pair of keys projecting radially        inwardly, the keys being positioned in spaced apart relation        from one another and defining a space therebetween, at least one        of the keys on one of the segments having a first camming        surface positioned adjacent to one end of the segment, the first        camming surface facing away from the space between the keys and        being angularly oriented relatively thereto;    -   positioning a first and a second of the pipe elements in        end-to-end relation;    -   positioning the plurality of segments surrounding ends of the        first and second pipe elements;    -   engaging the first camming surface with the groove in one of the        first and second pipe elements;    -   applying the fasteners to the segments; and    -   tightening the fasteners so as to draw the segments toward one        another, the first camming surface sliding into the groove and        thereby moving the first and second pipe elements away from one        another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a coupling for connecting two pipes endto end, the pipes being shown in phantom line;

FIG. 1A is a perspective view showing a detail of the coupling depictedin FIG. 1;

FIG. 2 is an exploded perspective view of the pipe coupling shown inFIG. 1;

FIG. 2A is an exploded perspective view of an alternate embodiment of apipe coupling according to the invention;

FIG. 2B is a perspective view of a portion of FIG. 2 shown on anenlarged scale;

FIG. 3 is a side view of a segment comprising the coupling shown in FIG.1;

FIG. 4 is a bottom view of the segment shown in FIG. 3;

FIG. 4A is a side view of an alternate embodiment of a segment havingone key and a flange for mating with flanged pipes or fittings;

FIG. 5 is a cross-sectional view taken at line 5-5 of FIG. 1;

FIGS. 5A and 5B are cross sectional views taken at line 5-5 of FIG. 1showing alternate embodiments of the coupling according to theinvention;

FIGS. 6 and 7 are side views of a roller tool forming a groove in apipe;

FIGS. 7A-7G show side views of various embodiments of roller tools forforming a groove in a pipe;

FIG. 8 is a cross-sectional view of an alternate embodiment of thecoupling;

FIG. 9 is a partial perspective view of an alternate embodiment of acoupling according to the invention;

FIGS. 10-15 are longitudinal sectional views of embodiments of pipeshaving circumferential grooves according to the invention; and

FIGS. 16-21 illustrate various fittings and components havingcircumferential grooves according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a pipe coupling 10 for connecting two pipes 12 and 14co-axially end to end. As shown in FIG. 2, coupling 10 is comprised ofat least two segments 16 and 18. Each segment 16 and 18 has lugs 20 and22 respectively, the lugs being positioned at or proximate to each endof the segments. The lugs 20 at each end of segment 16 align with thelugs 22 at each end of segment 18. Lugs 20 and 22 are adapted to receivefasteners, preferably in the form of bolts 24 and nuts 26 for joiningthe segments to one another end to end surrounding the pipes 12 and 14.In one embodiment, shown in FIG. 1, the lugs 20 engage the lugs 22 inwhat is known as “pad-to-pad engagement” with the lugs contacting oneanother when the segments 16 and 18 are properly engaged with the pipes12 and 14 as explained below. The lugs may also be attached to eachother in spaced apart relation when the segments 16 and 18 are properlyengaged with the pipes 12 and 14, as illustrated in FIG. 1A.

Although lugs are the preferred means for attaching the segments to oneanother end to end, it is recognized that there are other attachmentmeans, such as circumferential bands, axial pins, and latching handles.These means are disclosed in U.S. Pat. Nos. 1,541,601, 2,014,313,2,362,454, 2,673,102, 2,752,174, 3,113,791, and 4,561,678, all of whichare hereby incorporated by reference.

For large diameter pipes, it is sometimes advantageous to form thecoupling 10 from more than two segments. As shown in FIG. 2A, pipecoupling 10 comprises segments 16 a and 16 b joined to each other and tosegments 18 a and 18 b, also joined to one another. Each segment againpreferably has lugs 20 and 22 at each end thereof, the segments beingjoined to one another end to end by fasteners such as bolts 24 and nuts26. The following description of the coupling 10 is provided by way ofexample, and is based upon a coupling having two segments with lugs ateither end. Various aspects of the description are applicable toalternate embodiments regardless of the number of segments comprisingthe coupling or the manner in which the segments are attached to oneanother.

As shown in FIG. 2, each segment 16 and 18 has an arcuate surface 28facing inwardly toward pipes 12 and 14. A pair keys 30 project radiallyinwardly from the arcuate surface 28. Keys 30 on each segment are inspaced apart relation to one another and define a space 32 between them.As best shown in FIG. 5, to effect the connection between pipes 12 and14, keys 30 engage grooves 34 and 36 extending circumferentially aroundpipes 12 and 14 respectively. Engagement of keys 30 with grooves 34 and36 substantially rigidly connect the pipes 12 and 14 coaxially to oneanother and maintain them at a predetermined separation as indicated bythe gap 38. A sealing member 40 is positioned within space 32 andbetween the arcuate surfaces 28 of segments 16 and 18 and the pipes 12and 14. The gap 38 between the pipes 12 and 14 provides tolerancefacilitating mounting of the coupling and allows pressurized fluid toapply hydraulic pressure to the sealing member 40 and ensure a fluidtight seal between the pipes 12 and 14.

As best shown in FIGS. 2 and 3, each key 30 preferably has a pair ofcamming surfaces 42 positioned adjacent to lugs 20 and 22 or otherwisenear the ends of the segments. Camming surfaces 42 preferably faceoutwardly away from space 32 and are angularly oriented, as shown inFIG. 2B, with respect to an axis 43 oriented substantially tangential tothe key 30. The camming surfaces have an angular orientation 45 thatforms a wedge 46 adjacent to each lug, also shown in FIG. 4. As thesegments 16 and 18 are brought into engagement with grooves 34 and 36 toconnect pipe 12 to pipe 14 as illustrated in FIG. 5, the cammingsurfaces 42 (see FIG. 2) are the first surfaces to engage the grooves 34and 36. The wedge 46 formed by the camming surfaces 42 provides amechanical advantage which forces the pipes 12 and 14 apart from oneanother as the lugs 20 and 22 of segments 16 and 18 are brought towardone another, preferably into pad-to-pad engagement. This wedging actionensures that a separation gap 38 between the pipe ends (see FIG. 5) willbe achieved when the connection between the pipes 12 and 14 is effectedwhile reducing the force required to bring the lugs 20 and 22 towardeach other. Lugs 20 and 22 are normally drawn toward each other bytightening nuts 26 (see FIG. 1). The mechanical advantage obtained bythe use of wedge 46 significantly reduces the torque applied to nuts 26needed to bring the lugs 20 and 22 into pad-to-pad engagement toseparate the pipes 12 and 14 by the gap 38, and thereby allows largediameter, heavy pipes to be manually connected, even when stackedvertically above one another. Such configurations are a particularproblem as the insertion of the keys 30 into the grooves 34 and 36 mustlift the entire weight of the pipe to form the gap 38. The wedge 46makes this effort significantly easier. Preferably, as shown in FIG. 2B,the angular orientation 45 of camming surfaces 42, as measured withrespect to axis 43, is preferably about 5°, but may be up to about 10°for practical designs.

The use of keys having camming surfaces is not confined to couplings forjoining grooved pipes to one another, but may be used on practically anycoupling arrangement having at least one key. FIG. 4A shows a couplingsegment 51 used in conjunction with a similar coupling segment to attachgrooved pipe to flanged pipe. Coupling segment 51 has an arcuate key 30with camming surfaces 42 at either end. As described above, the cammingsurfaces may be angularly oriented tangentially with respect to the key30 and form a wedge 46 as shown in FIG. 4. Opposite the key is a flange53 adapted to engage a mating flange on a flanged pipe. The flanges aresecured via fasteners that pass though bolt holes 55 as is understoodfor flanged connections. The coupling segment 51 is attached end to endto its associated coupling segment by attachment means, preferably lugs20 positioned near the ends of the segment that align and are engaged byfasteners as is understood in the art and described above.

As best shown in FIGS. 5 and 5A, keys 30 preferably have a shape thatwill effect a wedging action when they engage grooves 34 and 36. FIG. 5illustrates one configuration wherein keys 30 have a wedge-shaped crosssection. The keys 30 are defined by an inner surface 50 facing space 32,an outer surface 52 facing outwardly away from space 32, and a radialsurface 54 positioned between the inner and outer surfaces and facingradially inwardly toward the pipes engaged by the coupling. Preferably,the inner surface 50 is oriented substantially perpendicularly to theaxis 48 and outer surface 52 is oriented angularly relative to the axis48 so as to form the wedge-shaped cross section of keys 30. The relativeangle 56, measured radially with respect to the key between the outersurface 52 and an axis 48 oriented substantially co-axially with thelongitudinal axes of pipes 12 and 14, ranges up to about 70°, although50° is preferred (see also FIG. 1).

Although surfaces 52 and 54 in FIG. 5 are shown in cross-section ashaving a straight profile, they may be, for example, convex, concave orhave some other profile shape and still effect a wedging action whenengaged with grooves 34 and 36. An alternate embodiment of keys 30 isillustrated in FIG. 5A wherein surface 50 has a curved cross sectionalprofile in the form of a convex radius that substantially blends intoradial surface 54.

As shown in FIG. 4, it is preferred that the radial angular orientation44 of camming surfaces 42 be substantially equal to the radial angularorientation 56 of the key outer surface 52 as measured relatively to thelongitudinal axis 48. It is advantageous to match the radial orientationangles of the camming surfaces 42 and the key outer surfaces 52 with oneanother to avoid point contact when the surfaces engage facing surfacesof the grooves 34 and 36 as the coupling is installed in order tomitigate gouging between the surfaces that results from point to pointcontact.

Preferably, the grooves 34 and 36 that keys 30 engage have a shape thatis complementary to the wedge-shape cross section of the keys. Ingeneral, it is advantageous that the keys have a cross sectional shapethat substantially fills the grooves even when the shapes of the grooveand key are not exactly complementary. Groove 36 is described in detailhereafter, groove 34 being substantially similar and not requiring aseparate description. Groove 36 is defined by a first side surface 58positioned proximate to end 14 a of pipe 14, a second side surface 60positioned in spaced apart relation to the first side surface 58 anddistally from the end 14 a, and a floor surface 62 that extends betweenthe first and second side surfaces. The complementary shape of thegroove 36 to the keys 30 is achieved by orienting the floor surface 62substantially parallel to the radial surface 54, orienting the firstside surface 58 substantially perpendicularly to the floor surface 62(and thus substantially parallel to the inner surface 50), and orientingthe second side surface 60 substantially parallel to the outer surface52 (and thus angularly to the floor surface 62).

Preferably, the keys 30 and the lugs 20 and 22 are sized and tolerancedso that when the lugs 20 are in pad-to-pad engagement with the lugs 22,i.e., in contact with each other as shown in FIG. 1, the keys 30 engagethe grooves 34 such that the keys' outer surface 52 is either justcontacting the second side surface 60 in what is called “line-on-lineclearance” (see the left halt of FIG. 5), or is in spaced relation tothe second side surface 60 of the groove, as defined by a gap 64 nogreater than 0.035 inches (shown on the right half of FIG. 5.Furthermore, the radial surface 54 is also in either line on lineclearance with the floor surface 62 (left half, FIG. 5), or in spacedrelation to floor surface 62, as defined by a gap 66 no greater than0.030 inches (right half, FIG. 5). The inner surface 50 is nominally incontact with the first side surface 58 as shown in FIG. 5, but there maybe a gap there as well for certain tolerance conditions. As a practicalmatter, however, it is difficult and costly to make pipes and couplingsperfectly round and to the exact dimensions desired, so that there willbe intermittent contact between various surfaces of the keys 30 andgrooves 34 and 36 circumferentially around any pipe joint, creating aneffectively rigid joint. Joint rigidity may be further augmented by theuse of teeth 31 that project outwardly from the various surfaces of keys30 as best shown in FIG. 2. Teeth 31 bite into the groove surfaces ofthe pipes, augmenting friction to help prevent rotational displacementof the pipes relatively to the couplings. The same relationships betweenthe various surfaces mentioned above may also be achieved when the lugsare attached to one another in spaced apart relation as shown in FIG.1A.

Analogous relationships between the key surfaces and the surfacescomprising the grooves are contemplated even when the keys do not have ashape complementary to that of the groove, as shown in FIG. 5A.Couplings having such keys, for example, the convex shaped key 30, mayhave surfaces 52 that just contact the second side surface 60 in line online clearance (left side, FIG. 5A), or be in spaced relation to surface60 (right side, FIG. 5A), having a gap 64 between the surfaces 52 and 60of about 0.035 inches. Again, surfaces 54 and 66 may also be in line online clearance or may be separated by a gap 62, preferably no greaterthan 0.030 inches.

Alternately, as shown in FIG. 5B, wedging action of keys 30 may also beensured when inner surface 50 and outer surface 52 contact groovesurfaces 58 and 60, respectively, but radial surface 54 is in spacedrelation to the groove's floor surface 62 with a gap 66. The right sideof FIG. 5B shows various straight sided key surfaces 50, 52 and 54 andcounterpart straight sided groove surfaces 58, 60 and 62 giving thegroove and the key substantially complementary shapes. The left side ofFIG. 5B shows a convexly curved outer surface 52 engaging a straightsurface 60, as an example wherein the shape of the key and the grooveare not substantially complementary. Note that groove floor surface 62is shown on the left side to be angularly oriented with respect to thesurface of pipe 12.

It is found that the preferred configuration defined by pad-to-padengagement of lugs 20 and 22 in conjunction with the toleranceconditions as describe above provides several advantages. The engagementof inner surface 50 with first side surface 58 forces pipes 12 and 14into substantially precise axial position relative to one another.Because these surfaces bear against one another when the coupling isinstalled on the pipes they will not shift axially when internal fluidpressure is applied. Thus, designers need not take into accountlengthening of the piping network due to internal pressure during use,thereby simplifying the design. The relatively small gaps 64 and 66(which could be zero) ensure adequate rigidity and prevent excessiveangular displacement between the pipes and the couplings, while thetolerances necessary to limit the gaps within the desired limits allowthe coupling 10 to be manufactured economically. It also allows thegrooves in the pipes, valves or other fittings to be manufacturedeconomically. The gaps work advantageously in conjunction with thenormally encountered out of roundness of practical pipes to provide arigid joint. The pad-to-pad engagement of lugs 20 and 22 provides areliable visual indication that the coupling 10 is properly engaged withthe pipes 12 and 14.

If it is desired to have a more flexible coupling 10 to allow greaterangular deflection, then the gaps 64 at one or both ends of the couplingmay be made larger than the aforementioned limit of 0.035 inches. Forflexible couplings, it is found advantageous to have gap 64 betweensurfaces 52 and 60 preferably be ½ of the size of gap 38 between theends of pipes 12 and 14 as shown in FIG. 5.

It is also feasible to have keys 30 engage grooves 34 and 36 without agap under all tolerance conditions. This configuration takes advantageof the wedging action of the keys to provide a rigid joint. It is notpractical, however, to have this configuration and also maintain pad topad engagement of lugs 20 and 22 because it is very difficult toeconomically manufacture couplings and pipes to the necessary tolerancesto ensure both pad to pad engagement and full contact circumferentialwedging engagement of the keys and grooves. For the configurationwherein pad-to-pad engagement is not nominally held, as shown in FIG. 9,it is preferred to employ a tongue 110 adjacent to the lug 20 on segment16 that fits into a recess 112 adjacent to lug 22 on segment 18. Thetongue prevents sealing member 40 from blowing out through a gap betweenthe lugs 20 and 22 when the joint is subjected to high internalpressure.

As illustrated in FIG. 6, groove 36 is advantageously formed by coldworking the material forming pipe 14. In a preferred embodiment, groove36 comprises a first side surface 37 positioned proximate to the end ofpipe 14, a second side surface 60 positioned in spaced apart relation tothe first side surface and distally to the end of the pipe, and a floor41 that extends between the first and second side surfaces. Preferably,the second side surface is angularly oriented relatively to the floor atan angle 43 that is than 90 degrees.

A roller tool 68 is used having a cross sectional shape at its peripherysubstantially identical to the desired shape of the groove. The rollertool 68 is forcibly engaged with the outer surface 70 of pipe 14 aroundits circumference, either by moving the roller tool around the pipe ormoving the pipe about its longitudinal axis 48 relatively to a rollertool. Preferably, a back-up roller 72 engages the inner surface 74 ofthe pipe 14 opposite to the roller tool 68. The pipe wall 76 iscompressed between the roller tool 68 and the back-up roller 72. Use ofthe back-up roller 72 provides a reaction surface for the roller tool.The back-up roller also helps ensure that accurate groove shapes areachieved by facilitating material flow during roll grooving.

During cold working to form the groove 36 having the angularly orientedsecond side surface 60, it is found that significant friction isdeveloped between the roller tool 68 and the pipe 14. The friction iscaused by the contact between the angled surface 78 on the roller tool68 that forms the angularly oriented second side surface 60 of groove36. Because it is angled, points along angled surface 78 are atdifferent distances from the axis of rotation 80 of roller tool 68. Dueto their different distances from the axis 80, each of the points on thesurface 78 will move relative to one another at a different linear speedfor a particular angular velocity of the roller tool 68. The pointsfarthest from the axis 80 move the fastest and the points closest to theaxis move the slowest. Thus, there is a velocity differential along theangled surface 78 which causes the surface to slip relatively to thesecond side surface 60 of groove 36 as the roller tool 68 rotatesrelatively to the pipe 14 to form the groove. The relative slippingbetween the roller tool and the pipe causes the friction. Excessive heatcaused by the friction can result in a break down of the roller toolbearing lubricants and make the roller tool too hot to handle whenchanging tools for a different size pipe. The roller tool must beallowed to cool before it can be changed, resulting in lost time.

To mitigate the generation of excessive heat, the roller tool 82, shownin FIG. 7, is used to form a groove 84 in pipe 14. In groove 84, thesecond side surface 86 has a first surface portion 88 oriented angularlyrelative to the floor surface 90, and a second surface portion 92,positioned adjacent to the floor surface 90 and oriented substantiallyperpendicular to it, thereby reducing the size of the angularly orientedsecond side surface 86. By reducing the size of the angled surfaceregions on both the roller tool 82 and the groove 84 the friction causedduring cold working to form the groove is reduced. The first surfaceportion 88, being angularly oriented, still provides the advantages asdescribed above for the second side surface 60. An example of a coupling10 engaging a groove 84 is shown in FIG. 8.

The roller tool 82 has a circumferential surface 94 with a crosssectional shape complementary to groove 84, the shape comprising a firstperimetral surface 99 oriented substantially perpendicularly to the axisof rotation 80 of roller tool 82, a second perimetral surface 98positioned in spaced relation to the first perimetral surface 96 andoriented substantially perpendicular to the axis 80, a radial surface100 extending between the first and second perimetral surfaces andoriented substantially parallel to axis 80, and an angled surface 102positioned adjacent to perimetral surface 100 and oriented angularly tothe axis 80. The angled surface 102 is preferably oriented up to about70° relatively to axis 80, and most preferably at about 50°. Surface 102slopes away from the second perimetral surface, thereby making contactwith the pipe when forming the groove 84.

Wedging action between the keys 30 and grooves in the pipes can beachieved for groove cross sectional shapes other than those describedabove. The main criterion for wedging action is that the width of thegroove at the surface of the pipe be greater than the width of thegroove at the floor of the groove. FIGS. 10-15 show various grooveconfigurations meeting this criteria. FIG. 10 shows a groove 114partially defined by a side portion 116 having a concave cross sectionalshape. FIG. 11 shows a groove 118 partially defined by a side portion120 having a convex cross-sectional shape. In FIG. 12, the groove 122 ispartially defined by a side portion 124 having first and second angledportions 124 a and 124 b, the first angled portion 124 a having agreater slope than the second angled portion 124 b. FIG. 13 shows agroove 126 partially defined by a side portion 128 having a first angledportion 128 a with a slope less than the second angled portion 128 b.Combinations of radius and angled portions are also feasible, as shownin FIG. 14, wherein groove 130 has a radius portion 132 and an angledportion 134. FIG. 15 illustrates an example of a groove 136 having awedge-shaped cross sectional profile, there being no floor portion ofany significance as compared with the other example grooves. The groove136 is defined by side portions 136 a and 136 b oriented angularly withrespect to one another. Common to all of the designs is thecharacteristic that the width 138 of the groove at the surface of thepipe is greater than the width 140 of the groove at the floor of thegroove. Note that, although it is preferred that the floor besubstantially parallel to the pipe surface, it may also be curved, asshown in FIG. 10, or non-existent, as shown in FIG. 15, which has nofloor, the floor width being essentially zero. The floor may also beangularly oriented as shown in FIG. 5B.

Roller tools for creating grooves as described above are shown in FIGS.7A-7G. In FIG. 7A, roller tool 101 is rotatable about axis 80 and has aradially facing surface portion 103 flanked by a first surface portion105 and a second surface portion 107. Roller surface portion 105 ispreferably oriented perpendicularly to axis 80 and results in theformation of a substantially vertical groove side surface. Rollersurface portion is concave and results in the convex groove side surface120 as shown in FIG. 11.

Similarly, roller tool 109, shown in FIG. 7B, has a radially facingsurface portion 111 extending between a perpendicular surface portion113 and a convex surface portion 115. Such a roller produces a groovewith a concave side surface 116 as shown in FIG. 10.

Additional roller embodiments 117 and 119, shown in FIGS. 7C and 7D,each have a surface portion 121 with a first face 123 angularly orientedwith respect to axis 80, and a second face 125, also angularly orientedwith respect to axis 80, but at a different angle. In roller tool 117,the slope of the first surface portion is greater than the slope of thesecond surface portion, and this roller produces a groove 122 as shownin FIG. 12. In roller tool 119, the slope of the first surface portionis less than the slope of the second surface portion, and this rollerproduces a groove 126, having an angularly oriented side surface 124 asshown in FIG. 13.

Roller tool 127, shown in FIG. 7E, has no radially facing surface, anangled surface 129 intersects with a surface portion 131 that issubstantially perpendicular to the axis of rotation 80. Roller tool 127is useful for creating the groove shown in FIG. 15.

Roller tool 133, shown in FIG. 7F, has a curved radially facing surface135 and an angularly oriented surface 135 as well as a perpendicularsurface 137. The curved surface may be convex, concave, sinusoidal,hyperbolic, or irregularly curved.

As shown in FIG. 7G, the roller 139 may have a radially facing surface141 that is angularly oriented with respect to the axis of rotation 80.A groove as shown in FIG. 5B is produced by such a tool.

While grooves adapted to achieve significant wedging action with thekeys of a coupling have been described applied to pipe ends, suchgrooves may also be used in conjunction with pipe fittings as well. Forexample, FIG. 16 shows an elbow fitting 140 having circumferentialgrooves 142 at either end. Grooves 142 may have any of the crosssectional profiles illustrated in FIGS. 5 and 10-15 or their variationsas described above. Similarly, the Tee fitting 144 shown in FIG. 17 hasgrooves 146, preferably adjacent to each of its ends, the grooves beingadapted to develop wedging action to couple the fitting to pipes orother fittings as described herein. FIG. 18 shows a fitting 148 having awedging groove 150 adjacent to one end and a flange 152 at the oppositeend. Fitting 148 allows a piping network using mechanical couplings tobe joined to another network coupled using flanges. Furthermore, asillustrated in FIGS. 19 and 20, other types of fittings such as areducer 154 (FIG. 19) used to join pipes having different diameters, ora nipple 156 (FIG. 20) may also benefit from having respective grooves158 and 160 that are like those illustrated and described above thatincrease the wedging action between the coupling and the groove toensure either a stiffer or more flexible joint, depending upon thetolerances of the coupling as described above.

As further shown in FIG. 21, components related to control of fluidflow, such as a valve 162 may also have grooves 164 that are like thosedescribed above to couple the valve to pipes, fittings or othercomponents using mechanical couplings as described herein.

Pipe couplings according to the invention incorporate the advantages ofa rigid or flexible connection with a reliable visual indicator forconfirming that the coupling properly engages the pipes to effect afluid tight joint. The couplings provide a mechanical advantage whichallows manual assembly of piping networks of substantial diameterdespite their weight. The couplings have tolerances allowing them to beeconomically produced and still yield a substantially rigid jointbetween pipes.

1. A method for connecting pipe elements together end-to-end, said pipeelements having circumferential grooves proximate to each end, saidmethod comprising: providing a coupling comprising a plurality ofsegments joined end-to-end by a plurality of adjustably tightenablefasteners, each of said segments having a pair of keys projectingradially inwardly, said keys being positioned in spaced apart relationfrom one another and defining a space therebetween, at least one of saidkeys on one of said segments having a first camming surface positionedadjacent to one end of said segment, said first camming surface facingaway from said space between said keys and being angularly orientedrelatively thereto; positioning a first and a second of said pipeelements in end-to-end relation; positioning said plurality of segmentssurrounding ends of said first and second pipe elements; engaging saidfirst camming surface with said groove in one of said first and secondpipe elements; applying said fasteners to said segments; and tighteningsaid fasteners so as to draw said segments toward one another, saidfirst camming surface sliding into said groove and thereby moving saidfirst and second pipe elements away from one another.
 2. The methodaccording to claim 1, further comprising positioning a sealing membersurrounding said ends of said first and said second pipe elements. 3.The method according to claim 1, further comprising placing ends of saidfirst and second pipe elements in abutting relationship.
 4. The methodaccording to claim 1, further comprising forming a groove in each ofsaid first and second pipe elements by forming a first side surfaceproximate to an end of said pipe elements, forming a second side surfacepositioned in spaced relation to said first side surface and distal tosaid end of said pipe, forming a floor that extends between said firstand second side surfaces, upon said engaging of said first cammingsurface with one of said grooves said camming surface contacting saidsecond side surface of said one groove.
 5. The method according to claim4, further comprising forming said first side surface substantiallyperpendicularly to a long axis of said pipe element.
 6. The methodaccording to claim 5, further comprising forming said second sidesurface at an angle relatively to said long axis of said pipe.
 7. Themethod according to claim 6, further comprising further tightening saidfasteners and thereby forcing said keys into said grooves.
 8. The methodaccording to claim 7, further comprising contacting said first sidesurfaces in each of said grooves with said keys.
 9. The method accordingto claim 8, wherein said segments further comprise lugs positioned ateach end thereof, said lugs being adapted to receive said fasteners, oneof said lugs on each of said segments being in facing relation with oneof said lugs on another of said segments, said method further includingtightening said fasteners so as to bring said lugs in facing relationinto contact with one another thereby forming a rigid joint.
 10. Amethod for connecting pipe elements together end-to-end, said pipeelements having circumferential grooves proximate to each end, saidmethod comprising: providing a coupling comprising first and secondsegments joined end-to-end by a plurality of adjustably tightenablefasteners, each of said segments having a pair of keys projectingradially inwardly, said keys being positioned in spaced apart relationfrom one another and defining a space therebetween, each of said keyshaving a first camming surface positioned adjacent to one end of saidsegment, and a second camming surface positioned adjacent to an oppositeend of said segment, said camming surfaces facing away from said spacebetween said keys and being angularly oriented relatively thereto;positioning a first and a second of said pipe elements in end-to-endrelation; positioning said first and second segments surrounding ends ofsaid first and second pipe elements; engaging said camming surfaces withsaid grooves in said first and second pipe elements; applying saidfasteners to said segments; and tightening said fasteners so as to drawsaid segments toward one another, said camming surfaces sliding intosaid grooves and thereby moving said first and second pipe elements awayfrom one another.
 11. The method according to claim 10, furthercomprising positioning a sealing member surrounding said ends of saidfirst and said second pipe elements.
 12. The method according to claim10, further comprising placing ends of said first and second pipeelements in abutting relationship.
 13. The method according to claim 10,further comprising forming a groove in each of said first and secondpipe elements by forming a first side surface proximate to an end ofsaid pipe elements, forming a second side surface positioned in spacedrelation to said first side surface and distal to said end of said pipe,forming a floor that extends between said first and second sidesurfaces, upon said engaging of said camming surfaces with said groovessaid camming surfaces contacting said second side surface of saidgrooves.
 14. The method according to claim 13, further comprisingforming said first side surfaces substantially perpendicularly to a longaxis of said pipe element.
 15. The method according to claim 14, furthercomprising forming said second side surfaces at an angle relatively tosaid long axis of said pipe.
 16. The method according to claim 15,further comprising further tightening said fasteners and thereby forcingsaid keys into said grooves.
 17. The method according to claim 16,further comprising contacting said first side surfaces in each of saidgrooves with said keys.
 18. The method according to claim 17, whereinsaid segments further comprise lugs positioned at each end thereof, saidlugs being adapted to receive said fasteners, one of said lugs on eachof said segments being in facing relation with one of said lugs onanother of said segments, said method further including tightening saidfasteners so as to bring said lugs in facing relation into contact withone another thereby forming a rigid joint.